Can Performing Morning Cardio on Empty Stomach (Fasted Cardio) Help Burn Fat?

Have you ever tried getting up first thing in the morning and exercising?  Would you be willing to try if you could possibly burn more fat?  I’d like to discuss the potential benefits of performing morning cardio on empty stomach.  In short, some studies have shown that fasted cardio and even fasted workouts lead to increased fat burn.  Others believe that exercise intensity is reduced in a fasted state and therefore fasted workouts aren’t as effective.  Still others argue that things like exercise on empty stomach result in muscle loss.  Who’s right?

The Benefits of Morning Cardio

The main argument for performing morning cardio is that your body has reduced glycogen (carb) levels meaning that you will burn fat faster.  If you’ve ever heard trainers say that you need to perform 20 minutes of cardio before you start burning fat, this is the implicit reason why.  If you eat first thing before exercising, your body’s glycogen stores will be full and you will have to burn through those before beginning fat burning.  Of course, this theory doesn’t just apply to morning cardio.  Performing either cardio or weight training in a fasted state, say 3-4 hours without eating, can offer similar fat burning benefits.  In theory, mornings work best because your body has had all night to deplete glycogen.

Workout before breakfast for potential fat burning benefits…how would you feel exercising after you ate this anyway…probably very sluggish!

The Drawbacks of Morning Cardio

As usual, I don’t believe in absolutes when it comes to any potentially biased studies.  There are a few general questions about the effectiveness of fasted cardio.  Some people theorize that whether you burn glycogen or burn fat, you’re still burning calories.  The simple equation for weight loss is to burn more calories than you eat.  Therefore fasted workouts shouldn’t provide any additional benefit beyond regular workouts.  Others argue whether glycogen levels are really reduced during sleep at all.  Can your body really deplete glycogen overnight when it is completely at rest?

Additionally, some people just naturally struggle to exercise first thing in the morning.  Convenience can be a big deterrent.  I avoided morning cardio for months after my son was born because I needed the extra sleep time.  Even now, I don’t perform strength training in the morning.  My muscles feel too tight, and I don’t have adequate time for a warm-up.  Cardio is easier because my legs are warmed up from my morning walk around the block with my dog.

Invalidated Arguments Against Fasted Workouts

There are two misconceptions about fasted workouts that need to be discussed.  The first is that you can’t exercise intensity in a fasted state.  The reason this is important is that more intense exercise results in EPOC and a significant calorie after burn effect.  This is the principle behind high intensity interval training (HIIT).  That being said, from a personal standpoint, I sprint just as fast in the morning as I do at night.  There is no change in intensity, even on intermittent fasting days.  There’s even a theory that fasted workouts can be more intense due to the fight or flight reaction.  In essence, your body’s survival mechanism kicks it up a notch to provide an extra oomph of energy.

Our hunter ancestors found the extra intensity to chase, or run away from, creatures like this despite being in a fasted state.

The second misconception about morning workouts is that you risk losing muscle.  I completely disagree with this as well.  Many bodybuilders ensure they have plenty of protein and carbs in their systems to provide their bodies will muscle building nutrients.  Of course, many bodybuilders eat constantly so it’s inevitable that they won’t be exercising in a fasted state.  However, there’s no reason for this type of calorie injection prior to working out.  As long as you’re adequately nourished over the course of the day and continue lifting heavier weights, you won’t lose muscle.  If you start to plateau and find that you lift less and less, then muscle loss might be a concern.  That is more likely due to losing too much weight too fast rather than performing morning cardio or fasted workouts though.

John Barban of the Adonis Effect provides a good viewpoint on fasted cardio.

Why Not Try Fasted Cardio?

While I think studies are mixed regarding fasted cardio and fasted workouts, there’s no downside to at least trying to exercise on empty stomach.  At best, you’ll increase fat burning.  At worst, you’ll continue to burn calories that you would have burned by exercising at a different time of day.  By no means will you have less intense workouts or lose muscle mass.  I’ve only just recently begun to perform morning cardio on empty stomach again.  It’s definitely a great way to start the day.